Liquid ejection head and manufacturing method thereof

The liquid ejection head includes a plurality of element substrates including first and second element substrates and an electrical wiring substrate. The first and second element substrates each has a heating element array in which a plurality of heating elements producing heat energy for liquid ejection is arrayed, an electrically conductive protection layer covering the plurality of heating elements, an insulating layer arranged between the plurality of heating elements and the electrically conductive protection layer, and a connecting terminal for connecting to the outside. The electrical wiring substrate is electrically connected with the first and second element substrates via the connecting terminal. On the first and second element substrates, the connecting terminal includes a connecting terminal for the electrically conductive protection layer, and the electrically conductive protection layer is electrically connected to a common wiring provided on the electrical wiring substrate via the connecting terminal.